Full Guides on Ram and Bios as I and many others came across a issue over the last few years since the Z390 MB. Four sticks of ram @ 4266 MHz even in the MB QVL no longer work in XMP 1 or 2 at least with my set up. I am not a over clock person and back then when the build was first done I had to come to this site for help. After weeks the correct person helped me with a manual OC and it was stable but fast forward a few years and I updated the bios thinking I could go back if it did not work so wrong . If I could go back to my old 602 bios I would as it worked / was very stable but I cant and stuck on the new bios and back to smashing my head on the desk trying to get my 4266 speeds back. Just because a manual OC works on one bios does not mean it will work on newest / last bios update for said MB and I knew that but did not know I could not go back to the old bios. Two things I learned from this old build I will Never buy Gskill ram again even if its in the QVL and never buy four sticks get two sticks if you want to use XMP. With my new build my biggest war was finding a updated windows as my windows CD was to old and could not install any drivers on my windows 10. My husband is like your old build is for the VR only you dont need the ram at 4266MHz and I am like I want it back as thats what I paid for. On a really happy note my new build is stable and I am rocking corsair ram again in two sticks on XMP.
Bios 602 and did a bios update doh
passed 8hr test on Karhu RamTest
Set to Manual OC
Dram Frequency 4266MHz
Dram voltage 1.45v
CPU VCCIO Voltage 1.25v
CPU System Agent Voltage 1.29v
Dram timing control 17-18-18-38
Mode1
Dram command rate set to 2N set dram current capability to 130%
.jpg "Raja"){kind=avatar}
